Study on Shear Strength of Unsaturated Red Clay with Triaxial Tests

Abstract

The subgrade of the most roads is easy to be of instability under the cyclic loading action of the vehicles with the soil unsaturated. The main idea of this paper is that researching the unsaturated red clay which is common in the subgrade building of Jiangxi province with the pressure plate test and triaxial shear test. And the main equipments are the pressure plate apparatus and triaxial shear apparatus. In the research, c,φ value of the unsaturated red clay under different confining pressure and matrix suction are obtained and it can be shown in the tests that with the same matrix suction, while clay content of the clay soil sample is small its volumetric water content is small; and with the same volume moisture content, with small clay content matrix suction of the soil sample is small similarly. At the same time, we found that within the low substrate suction range, with the change of the soil sample moisture content bigger and the smaller the clay content, the influence the increase of matrix suction on the volumetric moisture content is smaller; with the same clay content in soil samples, the bigger the matrix suction the greater the value of c, φ of the unsaturated red cohesive soil ;with the same matrix suction, the smaller the clay content of the soil, the greater the value of c and the smaller the value of φ.